[EXT4 set 4][PATCH 1/5] i_version:64 bit inode version

[Andrew Morton]

On Wed, 11 Jul 2007 15:05:27 +1000 Neil Brown <neilb at suse.de> wrote:

> 
> It just occurred to me:
> 
>  If i_version is 64bit, then knfsd would need to be careful when
>  reading it on a 32bit host.  What are the locking rules?
> 
>  Presumably it is only updated under i_mutex protection, but having to
>  get i_mutex to read it would seem a little heavy handed.
> 
>  Should it use a seqlock like i_size?
>  Could we use the same seqlock that i_size uses, or would we need a
>  separate one?
> 

seqlocks are a bit of a pain to use (we've had plenty of deadlocks on the
i_size one).  We could reuse inode.i_lock for this modification.  Its
mandate is "general purpose innermost lock to protect stuff in this inode".